To apply a spoken dialog system to various domain tasks, it is effective to separate dialog knowledge about an applied domain task and a dialog processing engine for processing dialog using the dialog knowledge. A related art entitled “The rave claw dialog management framework: architecture and system (computer speech & language, 2009)” has proposed a dialog processing engine based on a task-independent and reusable dialog plan by proposing a dialog plan based task independent dialog management framework. In general, to provide a successful dialog service in a spoken dialog system, dialog knowledge (a domain meaning system, a task dialog flow, a dialog generation pattern, an application domain knowledge database (DB), and the like) suitable for a domain task and well defined is required. An operation of preparing dialog knowledge suitable for each domain task to be fitted for a given engine system requires a large amount of time and great effort. It is very difficult to construct a dialog managing engine without clearly knowing the contents of the dialog managing engine. The related art reuses an engine by simply separating the engine and knowledge and thus, may not reuse dialog knowledge of a domain task that increases efficiency of a dialog knowledge engine, which requires great effort.
The related art does not provide a scheme of packaging knowledge for each subtask of a domain task and does not provide a method capable of creating a new application domain by combining subtasks.
According to the related, spoken dialog systems use only a dialog management technology only for a response of a system to a user utterance and dialog progress and thus, do not have information about how a user induces or proceeds with a dialog after a system speech.
In a portion of spoken dialog systems, when a current system speech is a question, it is possible to know that a subsequent user utterance is an appropriate answer to the question. However, except for such fragmentary and partial dialog connection information, there is no information about how the user proceeds with a dialog throughout the entire domain task. That is, there is no information about what kind of question or content the user will request in a current situation. In the above unilateral system dialog management, leakage of dialog progress information on a user side about an application task causes unnecessary dialog between a system and a user to proceed, thereby decreasing availability of the spoken dialog system. When it is possible to provide information about how to proceed with a dialog, which may quickly and accurately complete the dialog in the given application on the user side, the spoken dialog system may be more conveniently used by providing a user dialog on the user side. Currently, the application range of the spoken dialog system has been expanded to a spoken dialog system for foreign language education as well as a spoken dialog interface in a mobile environment. When the spoken dialog system for foreign language education may propose various user dialogs and estimate a dialog length until a task is completed by each proposed user dialog, it is possible to variously teach foreign language by guiding a user to various dialog flows.